Both fft() and ifft() functions have an optional argument "number of points". If it is specified and it is bigger than the signal length, the signal will be extended with zeros. This can help provide better resolution.
If the argument is less than the number of points in the signal, it will be ignored.

There is no normalization factor included in the FFT. The normalization is done in IFFT.

NOTE: The FFT is the fastest possible for signals of power-of-2 length.